Novel mixed ester O-quinone photosensitizers

ABSTRACT

The invention relates to new mixed ester photosensitive compounds and photosensitizer compositions comprised thereof. The photosensitive compounds and photosensitizer compositions are prepared by condensing phenolic compounds with a 1,2-naphthoquinonediazide-4-sulfonic acid halide and an organic acid halide in specific ratios. Photoresist compositions comprising the photosensitive compounds and photosensitizer compositions are also disclosed. The photosensitizer compositions exhibit excellent solution stability and resistance to precipitation when formulated in alkali-soluble resin photoresist compositions. The photoresist compositions have improved shelf life.

BACKGROUND OF THE INVENTION

The present invention relates generally to photosensitive compositionsand radiation sensitive positive photoresist compositions andparticularly to compositions containing novolak and polyvinyl phenolresins together with naphthoquinone diazide sensitizing agents.

It is well known in the art to produce positive photoresist formulationssuch as those described in U.S. Pat. Nos. 3,666,473, 4,115,128,4,173,470 and 4,550,069. These include alkali-soluble novolak resinstogether with light-sensitive materials, usually a substitutednaphthoquinone diazide compound. The resins and sensitizers aredissolved in an organic solvent or mixture of solvents and are appliedas a thin film or coating to a substrate suitable for the particularapplication desired.

The novolak or polyvinyl phenyl resin component of these photoresistformulations is soluble in aqueous alkaline solutions, but thenaphthoquinone sensitizer acts as a dissolution rate inhibitor withrespect to the resin. Upon exposure of selected areas of the coatedsubstrate to actinic radiation, however, the sensitizer undergoes aradiation induced structural transformation and the exposed areas of thecoating are rendered more soluble than the unexposed areas. Thisdifference in solubility rates causes the exposed areas of thephotoresist coating to be dissolved when the substrate is immersed inalkaline developing solution while the unexposed areas are largelyunaffected, thus producing a positive relief pattern on the substrate.

In most instances, the exposed and developed substrate will be subjectedto treatment by a substrate-etchant solution. The photoresist coatingprotects the coated areas of the substrate from the etchant and thus theetchant is only able to etch the uncoated areas of the substrate, whichin the case of a positive photoresist, correspond to the areas that wereexposed to actinic radiation. Thus, an etched pattern can be created onthe substrate which corresponds to the pattern of the mask, stencil,template, etc., that was used to create selective exposure patterns onthe coated substrate prior to development.

The relief pattern of photoresist on substrate produced by the methoddescribed above is useful for various applications including, forexample, as an exposure mask or a pattern such as is employed in themanufacture of miniaturized integrated electronic components.

The properties of a photoresist composition which are important incommercial practice include the photospeed of the resist, developmentcontrast, resist resolution, and resist adhesion.

Photospeed is important for a photoresist, particularly in applicationswhere a number of exposures are needed, for example, in generatingmultiple patterns by a repeated process, or where light of reducedintensity is employed such as in projection exposure techniques wherethe light is passed through a series of lenses and mono-chromaticfilters. Thus, increased photospeed is particularly important for aresist composition employed in processes where a number of multipleexposures must be made to produce a mask or series of circuit patternson a substrate.

Development contrast refers to a comparison between the percentage offilm loss in the exposed area of development with the percentage of filmloss on the unexposed area. Ordinarily, development of an exposed resistcoated substrate is continued until the coating on the exposed area issubstantially completely dissolved away and thus, development contrastcan be determined simply by measuring the percentage of the film coatingloss in the unexposed areas when the exposed coating areas are removedentirely.

Resist resolution refers to the capability of a resist system toreproduce the smallest equally spaced line pairs and intervening spacesof a mask which is utilized during exposure with a high degree of imageedge acuity in the developed exposed spaces.

In many industrial applications, particularly in the manufacture ofminiaturized electronic components, a photoresist is required to providea high degree of resolution for very small line and space widths (on theorder of one micron or less).

The ability of a resist to reproduce very small dimensions, on the orderof a micron or less, is extremely important in the production of largescale integrated circuits on silicon chips and similar components.Circuit density on such a chip can only be increased, assumingphotolithography techniques are utilized, by increasing the resolutioncapabilities of the resist.

In order to achieve the desired sensitivity and contrast, it isnecessary to have a sufficiently high concentration of photosensitivecompounds in the photoresist to prevent dissolution of the unexposedresist during development. High concentrations photosensitizer may beachieved by dissolving a mixture of highly soluble and less solublephotosensitizers in the photoresist solution or by supersaturating thephotoresist solution with a photosensitizer.

However, solution concentration of photosensitizer near saturation canlead to a short shelf life due to solution instability and precipitationof the sensitizer prior to or during the use of the product. Thisphenomenon is referred to in U.S. Pat. Nos. 4,397,937 and 4,526,856,both of which are hereby incorporated by reference.

An important group of photosensitizers are the condensation products of1,2-naphthoquinonediazide-4-sulfonic acid and aromatic diols andpolyols. These compounds tend to exhibit superior photospeed andcontrast in the mid-UV region of the light spectrum when formulated inphotoresist compositions. However, these photosensitizers also tend tohave low solubility and solution stability.

Clecak et al. in U.S. Pat. No. 4,397,937 discloses improved solubilityby using as a sensitizer a bisester of 1-oxo-2-diazonaphthalene sulfonicacid and an unsymmetrical primary or secondary aliphatic diol which is amixture of geometric and diastereoisomers. Esterification of thealiphatic diol at one end with a diazonaphthoquinone molecule having theacid group in the 5 position and at the other end with adiazonophthoquinone molecule having the sulfonyl group in the 4 positionis disclosed. However, the patent emphasizes the importance of limitingthe invention to unsymmetrical aliphatic diols. Clecak et al. does notdisclose mixed esters of o-quinone diazide acids and non-light-sensitiveorganic acids.

According to Lewis et al. in U.S. Pat. No. 4,526,856, the problem ofobtaining higher concentrations of sensitizer was addressed by modifyingthe solvent system of the photoresist formulations. The solventcomposition which consists of cyclopentanone, or cyclopentanone andcyclohexanone with an aliphatic alcohol, when used in certain criticalratios provides good solubility.

In contrast, the present invention provides photosensitizers which arethe condensation products of 1,2naphthoquinonediazide-4-sulfonic acidand organic acids with aromatic diols and polyols. The photosensitizercompositions of the invention exhibit excellent solubility andresistance to precipitation when formulated in photoresist compositions.Also they may be dissolved into photoresist compositions at highersolution concentrations than previously known comparablephotosensitizers. The photoresist compositions of the invention exhibitexcellent solution stability and an improved shelf life. At the sametime they retain photosensitivity and contrast properties comparable tothe best formulations heretofore available.

SUMMARY OF THE INVENTION

The invention relates to new mixed ester photosensitive compounds andphotosensitizer compositions comprised thereof. The photosensitivecompounds and photosensitizer compositions are prepared by condensingphenolic compounds with a 1,2-naphthoquinonediazide-4-sulfonic acidhalide and an organic acid halide in specific ratios. Photoresistcompositions comprising the photosensitive compounds and photosensitizercompositions are also disclosed. The photosensitizer compositionsexhibit excellent solution stability and resistance to precipitationwhen formulated in alkali-soluble resin photoresist compositions. Thephotoresist compositions have improved shelf life.

According to the present invention there is provided: photosensitivecompounds represented by the general formulae (1), (2) or (3): ##STR1##wherein R is H, --X--R_(b) or ##STR2## X is a single C--C bond, --O--,--S--, --SO₂ --, ##STR3## n is 1 or 2, R_(a) is H, --OH, --OY, --OZ,halogen or lower alkyl, with at least one R_(a) radical being --OY andat least one thereof being --OZ, R_(b) is H, alkyl, aryl, substitutedalkyl, or substituted aryl; ##STR4## wherein R₁ is H, or ##STR5## Rc isH, --OH, --OY or --OZ, with at least one R_(c) radical being --OY and atleast one thereof being --OZ; and ##STR6## wherein R₂ is H, alkyl, aryl,substituted alkyl, or substituted aryl, R_(d) is --OH, --OY or --OZ withat least one R_(d) radical being --OY and at least one thereof being--OZ;

wherein Y is 1,2-naphthoquinonediazide-4-sulfonyl and Z is --W--R₃,where W is ##STR7## or --SO₂ --, and R₃ is alkyl, aryl, substitutedalkyl or substituted aryl.

According to the present invention there is provided: a photosensitizercomposition comprising the condensation product of:

(I) a phenolic compound selected from the group consisting of: ##STR8##wherein R is H, --X--R_(b), or ##STR9## R_(a) is H, --OH, halogen orlower alkyl, with at least two and not greater than six R_(a) radicalsbeing --OH, X is a single C--C bond, --O--, --S--, --SO₂ --, ##STR10## nis 1 or 2, R_(b) is H, alkyl, aryl, substituted alkyl or substitutedaryl; ##STR11## wherein R₁ is H or ##STR12## R_(c) is H or --OH with atleast two R_(c) radicals being --OH; and ##STR13## wherein R₂ is H,alkyl, aryl, substituted alkyl, or substituted aryl;

(II) a 1,2-naphthoquinonediazide-4-sulfonic acid (Diazo); and

(III) an organic acid halide represented by the formula:

    W--R.sub.3

wherein W is ##STR14## or --SO₂ --V, V is halogen, R₃ is alkyl, aryl,substituted alkyl or substituted aryl;

wherein the molar ratio of the amount of Diazo reacted to the amount oforganic acid reacted is in the range of from about 1:1 to about 39:1.

According to the present invention there is provided: a process forpreparing a photosensitizer composition comprising: condensing aphenolic compound represented by the general formulae (A), (B) or (C):##STR15## wherein R is H, --X--R_(b), or ##STR16## R_(a) is H, --OH,halogen or lower alkyl, with at least two and not greater than six R_(a)radicals being --OH, X is a single C--C bond, --O--, --S--, --SO₂ --,##STR17## n is 1 or 2, R_(b) is H, alkyl, aryl, substituted alkyl orsubstituted aryl; ##STR18## wherein R₁ is H or ##STR19## R_(c) is H or--OH with at least two R_(c) radicals being --OH, and ##STR20## whereinR₂ is H, alkyl, aryl, substituted alkyl, or substituted aryl; with a1,2-napthoquinonediazide-4-sulfonic acid (Diazo) and with an organicacid halide represented by the formula W--R₃, wherein W is ##STR21## or--SO₂ --V, V is halogen, R₃ is alkyl, aryl, substituted alkyl orsubstituted aryl; wherein the molar ratio of the amount of Diazo to theamount of organic acid halide to be reacted is in the range of fromabout 1:1 to about 39:1.

According to the present invention there is provided: a photoresistcomposition comprising in admixture a novolak or polyvinyl phenol resin,a photosensitive compound as described above, and a solvent.

According to the present invention there is provided: a photoresistcomposition comprising in admixture a novolak or polyvinyl phenol resin,a photosensitizer composition as described above, and a solvent.

According to the present invention there is provided: a method forproducing an article which comprises coating a photoresist compositionas described above onto a substrate; imagewise exposing said compositionto sufficient ultraviolet radiation to render said imagewise exposedportions substantially soluble in an aqueous alkaline solution; and thenremoving the thusly exposed composition portions from said substratewith an aqueous alkaline developing solution.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention overcomes problems of sensitizer precipitation,solution instability and short shelf life of photoresist formulations bychemically modifying the photosensitizer component of the photoresistcompositions. It has been found that by substituting an organic acid fora portion of the 1,2-naphthoquinonediazide-4-sulfonyl groups (Diazo) inphotosensitizer compositions consisting essentially of1,2-naphthoquinonediazide-4-sulfonyl esters of phenolic compounds, novelmixed ester photosensitive compounds and photosensitizer compositionsmay be obtained. These Diazo/organic acid mixed esters andphotosensitizer compositions thereof may be formulated inpositive-acting alkali-soluble novolak or polyvinyl phenol resinphotoresist compositions which exhibit improved shelf life and solutionstability while maintaining photosensitivity and development contrastproperties comparable to photoresist compositions formulated withphotosensitizer compositions of unmodified Diazo esters.

The photosensitive compounds and photosensitizer compositions may beobtained by condensing phenolic compounds with a mixture of Diazo andorganic acid halides. The molar ratio of the amount of Diazo to theamount of organic acid halide in the mixture may be in the range of fromabout 1:1 to about 39:1, preferably from about 4:1 to about 19:1, ormore preferably from about 93:7 to about 85:15. For example, one mole of2,3,4-trihydroxybenzophenone may be condensed with a 9:1 mixture of 2.7moles of Diazo and 0.3 moles of methanesulfonyl chloride to yield aphotosensitizer composition comprising compounds having the formula:##STR22## where R₁, R₂ and R₃ may independently be either1,2-naphthoquinonediazide-4-sulfonyl (Diazo) or methanesulfonyl.

Thus, in one aspect, the invention provides photosensitive compoundsuseful in photosensitizer compositions. The photosensitive compounds maybe represented by general formulae (1), (2) and (3): ##STR23## wherein Ris H, --X--R_(b) or ##STR24## X is a single C--C bond, --O--, --S--,--SO₂ --, ##STR25## n is 1 or 2, R_(a) is H, --OH, --OY, --OZ, halogen,preferably Cl or Br, or lower alkyl, preferably lower alkyl having 1-4carbon atoms, with at least one R_(a) radical being --OY and at leastone thereof being --OZ, R_(b) is H, alkyl, aryl, substituted alkyl, orsubstituted aryl; preferably alkyl having 1-20 carbon atoms, morepreferably 1-12 carbon atoms, preferably aryl being phenyl or naphthyl,alkyl or aryl may be substituted with lower alkyl having 1-4 carbonatoms, lower alkoxy having 1-4 carbon atoms, or halogen atoms,preferably Cl or Br; ##STR26## wherein R₁ is H, or ##STR27## R_(c) is H,--OH, --OY or --OZ, with at least one R_(c) radical being --OY and atleast one thereof being --OZ; and ##STR28## wherein R₂ is H, alkyl,aryl, substituted alkyl, or substituted aryl, R_(d) is --OH, --OY or--OZ with at least one R_(d) radical being --OY and at least one thereofbeing --OZ; the alkyl radicals R₂ may be straight-chain or branched andmay be substituted with halogen atoms or lower alkoxy groups having 1-4carbon atoms, preferably the alkyl radicals have 1-20 carbon atoms; thearyl radicals R₂ are preferably mononuclear and may be substituted withlower alkyl or alkoxy groups having 1-4 carbon atoms or with halogenatoms, preferably the aryl radicals have 1 to 10 carbon atoms; compoundsin which R₂ is an aryl radical are particularly preferred and compoundsin which the aryl radical is a phenyl radical are especially preferred;

wherein Y is 1,2-naphthoquinonediazide-4-sulfonyl and Z is --Z--R₃,where W is ##STR29## or --SO₂ --, and R₃ is alkyl, aryl, substitutedalkyl or substituted aryl; the alkyl radicals R₃ may be straight-chainor branched and may be substituted with halogen atoms, preferably Br orCl, or lower alkoxy groups having 1-4 carbon atoms, preferably alkylhaving 1-20 carbon atoms; the aryl radicals R₃ are preferablymononuclear and may be substituted with lower alkyl or alkoxy groupshaving 1-4 carbon atoms or with halogen atoms, preferably Br or Cl,preferably aryl radicals having 6-10 carbon atoms; phenyl radicals arepreferred; alkyl radicals are particularly preferred and lower alkylradicals having 1-6 carbon atoms are especially preferred.

These photosensitive compounds may be prepared, for example, in themanner as herein described for the preparation of the photosensitizercompositions. The compounds may be isolated and purified as desired.

Another aspect of the invention provides photosensitizer compositionscomprising inter alia the photosensitive compounds disclosed herein. Thephotosensitizer compositions may be obtained by condensing phenoliccompounds with a mixture of Diazo and organic acid halides. The Diazocomponent and the organic acid halide component of the mixture may becondensed either sequentially or concurrently with the phenoliccompounds.

The Diazo/organic acid mixture may be reacted preferably instoichiometric quantities with the hydroxyl-bearing compounds. However,the phenolic compounds need not be completely esterified and less thanstoichiometric quantities of the Diazo and organic acid halide compoundsmay be condensed with the phenolic compounds provided that the molarratio of Diazo to organic acid halide reacted is within the rangesspecified herein. The total amount of Diazo and organic acid halidereacted with the phenolic compounds should be sufficient to produce aphotosensitizer composition capable of inhibiting the dissolution rateof an alkali-soluble resin.

The phenolic compounds which may be condensed with the Diazo/organicacid mixture are represented by the general formulae (A), (B) and (C):##STR30## wherein R is --H, --OH, --X--R_(b), or ##STR31## R_(a) is H,--OH, halogen, preferably Cl or Br, or lower alkyl, preferably loweralkyl having 1 to 4 carbon atoms; with at least two and not greater thansix R_(a) radicals being --OH, X is a single C--C bond, --O--, --S--,--SO₂ --, ##STR32## n is 1 or 2, R_(b) is H, alkyl, aryl, substitutedalkyl or substituted aryl; preferably alkyl having 1-20 carbon atoms,more preferably 1-12 carbon atoms, preferably aryl being phenyl ornaphthyl, alkyl or aryl may be substituted with lower alkyl having 1-4carbon atoms, lower alkoxy having 1-4 carbon atoms, or halogen atoms,preferably Cl or Br; ##STR33## wherein R₁ is H or ##STR34## R_(c) is Hor --OH with at least two R_(c) radicals being --OH; and ##STR35##wherein R₂ is H, alkyl, aryl, substituted alkyl, or substituted aryl;the alkyl radicals R₂ may be straight-chain or branched and may besubstituted with halogen atoms or lower alkoxy groups having 1-4 carbonatoms, preferably the alkyl radicals have 1-20 carbon atoms; the arylradicals R₂ are preferably mononuclear and may be substituted with loweralkyl or alkoxy groups having 1-4 carbon atoms or with halogen atoms,preferably the aryl radicals have 1 to 10 carbon atoms; compounds inwhich R₂ is an aryl radical are particularly preferred and compounds inwhich the aryl radical is a phenyl radical are especially preferred.

Among the phenolic compounds represented by the general formula (I) are:hydroxyl-bearing benzene compounds such as 1,2-dihydroxybenzene,1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 1,2,3-trihydroxybenzene,1,2,4-trihydroxybenzene, 1,3,5-trihydroxybenzene, and the like;dihydroxybenzophenones such as 2,2'-dihydroxybenzophenone,2,3'-dihydroxybenzophenone, 2,4-dihydroxybenzophenone,2,4'-dihydroxybenzophenone, 2,5-dihydroxybenzophenone,3,3'-dihydroxybenzophenone, 4,4'-dihydroxybenzophenone, and the like;trihydroxybenzophenones such as 2,2',6-trihydroxybenzophenone,2,3,4-trihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone,2,4,6-trihydroxybenzophenone, 3,4,5-trihydroxybenzophenone, and thelike; tetrahydroxybenzophenones such as2,2'3,4-tetrahydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone,2,2'4,6'-tetrahydroxybenzophenone, 2,2',5,6'-tetrahydroxybenzophenone,2,3',4,4'-tetrahydroxybenzophenone, 2,3',4,6-tetrahydroxybenzophenone,2,4,4',6-tetrahydroxybenzophenone, 3,3',4,4',-tetrahydroxybenzophenone,and the like; pentahydroxybenzophenones; hexahydroxybenzophenones;dihydroxy- and trihydroxy-phenyl alkyl ketones such as2,4-dihydroxphenyl alkyl ketones, 2,5-dihydroxyphenyl alkyl ketones,3,4-dihydroxyphenyl alkyl ketones, 3,5-dihydroxyphenyl alkyl ketones,2,3,4-trihydroxyphenyl alkyl ketones, 3,4,5-trihydroxyphenyl alkylketones, 2,4,6-trihydroxyphenyl alkyl ketones, and the like, preferablyalkyl having 1-12 carbon atoms such as methyl, ethyl, butyl, n-hexyl,heptyl, decyl, dodecyl, and the like; dihydroxyphenyl aralkyl ketones;trihydroxyphenyl aralkyl ketones; dihydroxydiphenyls;trihydroxydiphenyls such as 2,2',4-trihydroxydiphenyl;tetrahydroxydiphenyls such as 2,2',4,4'-tetrahydroxydiphenyl;dihydroxydiphenyl oxides; dihydroxydibenzyl oxides; dihydroxydiphenylalkanes, preferably lower alkanes such as methane, ethane, propane orthe like; dihydroxybenzoic acid; trihydroxybenzoic acids; dihydroxy- andtrihydroxy-benzoic acid alkyl esters, alkyl preferably having 1 to 12carbon atoms, such as n-butyl 2,4-, 2,5-, 3,4- and3,5-dihydroxybenzoate, 2,4,4-trimethylpentyl 2,4-dihydroxybenzoate, andthe like; dihydroxy- and trihydroxy-benzoic acid phenyl esters;dihydroxy-, trihydroxy-, and tetrahydroxy-diphenyl sulfides such as4,4'-dihydroxydiphenyl sulfide; dihydroxydiphenyl sulfones; anddihydroxy- and trihydroxy-phenyl naphthyl ketones such as2,3,4-trihydroxyphenyl naphthyl ketone; and the like.

Examples of compounds of general formula (I) where at least one R_(a)radical is halogen or lower alkyl include2,4-dihydroxy-3,5-dibromobenzophenone; 5-bromo-2,4-dihydroxybenzoic acidand esters; 2,4,2',4'-tetrahydroxy-3,5,3',5'-tetrabromodiphenyl;4,4'-dihydroxy-2,2'dimethyl-5,5'-di-tert.-butyl diphenyl;4,4'-dihydroxy-2,2'dimethyl-5,5'-di-tert.-butyl diphenyl sulfide;2,4,2',4'-tetrahydroxy-3,5,3'5'-tetrabromodiphenyl sulfone; and thelike.

The preferred class of phenolic compounds of general formula (I) are thehydroxyl-bearing benzophenones and the especially preferred compoundsare the trihydroxybenzophenones.

Among the phenolic compounds represented by general formula (II) are:dihydroxynaphthalenes such as 1,2-dihydroxynaphthalene,1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene,1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene,1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene,2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, and the like;dihydroxydinaphthylmethanes such as 2,2'-dihydroxydinaphthylmethane, andthe like. The dihydroxynaphthylenes are preferred. The hydroxyl groupsof the dihydroxynaphthylenes may be either on the same nucleus or ondifferent nucleii of the naphthalene moiety.

Among the phenolic compounds represented by general formula (III) arebis-(3-benzoyl-4,5,6-trihydroxyphenyl)-methane;bis-(3-acetyl-4,5,6-trihydroxyphenyl)-methane;bis-(3-propionyl-4,5,6-trihydroxyphenyl)-methane;bis-(3-butyryl-4,5,6-trihydroxyphenyl)-methane;bis-(3-hexanoyl-4,5,6-trihydroxyphenyl)-methane;bis-(3-heptanoyl-4,5,6-trihydroxyphenyl)-methane;bis-(3-decanoyl-4,5,6-trihydroxyphenyl)-methane;bis-(3-octadecanoyl-4,5,6-trihydroxyphenyl)-methane; and the like.

The organic acid halides which may be used to modify the Diazo estercompounds may be represented by the formula:

    W--R.sub.3

wherein W is ##STR36## or --SO₂ --V, V is halogen, preferably Cl or Br,and R₃ is alkyl, aryl, substituted alkyl or substituted aryl; the alkylradicals R₃ may be straight-chain or branched and may be substitutedwith halogen atoms, preferably Br or Cl, or lower alkoxy groups having1-4 carbon atoms, preferably the alkyl radicals have 1-20 carbon atoms,the aryl radicals R₃ are preferably mononuclear and may be substitutedwith lower alkyl or alkoxy groups having 1-4 carbon atoms or withhalogen atoms, preferably Br or Cl, preferably the aryl radicals have 6to 10 carbon atoms, phenyl radicals are especially preferred; compoundsin which R₃ is an alkyl radical are particularly preferred and compoundsin which the alkyl radical is lower alkyl radical having 1-6 carbonatoms are especially preferred.

Among the organic acid halides represented by the above formula arealkyl sulfonyl halides such as methanesulfonyl chloride, ethanesulfonylchloride, propanesulfonyl chloride, n-butanesulfonyl chloride,dodecanesulfonyl chloride, and the like; arylsulfonyl chlorides such asbenzenesulfonyl chloride, naphthalenesulfonyl chlorides, and the like;acyl halides such as acetyl chloride, butanoyl chloride, valerylchloride, benzoyl chloride, benzoyl bromide, naphthoyl chlorides, andthe like.

The preferred organic acid halides are lower alkyl sulfonyl halides andlower alkyl acyl halides having 1-6 carbon atoms, and benzenesulfonylhalides and benzoyl halides. These acid halides may be substituted orunsubstituted.

The following examples are presented solely to illustrate the inventionand should not be considered to constitute limitations on the invention,many variations of which are possible without departing from the spiritor scope thereof.

PREPARATION OF PHOTOSENSITIZER COMPOSITIONS

The preparation of naphthoquinonediazide photosensitizers is describedin U.S. Pat. Nos. 3,046,118, 3,106,645 and 4,397,937, which are herebyincorporated by reference. The photosensitizer compositions of thisinvention may be obtained by condensing the desirednaphthoquinonediazide sulfonyl halide and organic acid halide with aphenolic compound which has more than one hydroxyl group in the presenceof an acid scavenger. The resulting sensitizer composition may bepurified as desired.

Solvents for the reaction may include, but are not limited to, acetone,p-dioxane, tetrahydrofuran, methylene chloride, pyridine, or the like.

The acid scavenger may be inorganic, such as sodium carbonate, or thelike, or organic, such as sodium salts of weak acids, tertiary aminessuch as triethyl amine, pyridines, or the like.

EXAMPLE 1

A ten mole percent methanesulfonyl-modified2,3,4-trihydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acidtriester is prepared. 23.0 grams of 2,3,4-trihydroxybenzophenone and72.6 grams of 1,2-naphthoquinonediazide-4-sulfonyl chloride (Diazo) arestirred together in 350 ml acetone. 3.6 grams of methanesulfonylchloride are added in. 36.4 grams of triethylamine are slowly dropped inwhile maintaining an internal temperature of about 30° C. The reactionmixture is cooled to ≦15° C., treated with charcoal and diatomaceousearth, filtered, washed with 350 ml acetone, and drowned in 3.5 litersof 1 normal hydrochloric acid. The product is filtered off, washed withwater, and dried in an air oven at ≦40° C. The yield obtained is 85.9grams, 97.5% of theory.

The product thusly obtained may be purified as desired.

The method of synthesis shown in this example is not the only way tomake such photosensitizer compositions, as those skilled in the art mayobtain comparable products by simply varying solvents, bases or reactionconditions. Several other examples were prepared according to the abovemethod at various molar ratios of Diazo to organic acid halide and areset forth in Tables 1 and 2.

COMPARATIVE EXAMPLES

Several comparative examples are prepared by condensing2,3,4-trihydroxybenzophenone with 1,2-naphthoquinonediazide-4-sulfonylchloride in a molar ratio of 1 to 3.

PREPARATION OF POSITIVE PHOTORESIST SYSTEMS

The photoresist composition may be prepared by formulating thephotosensitizer compositions of this invention with alkali-solubleresins, solvents and, if desired, other additives. Alkali-soluble resinswhich may be used include, for example, novolak resins, polyvinyl phenolresins, and the like. Alkali-soluble novolak resins, which may be usedfor preparing photosensitive compositions, are known in the art. Aprocedure for their manufacture is described in Chemistry andApplication of Phenolic Resins, Knop, A. and Scheib, W.; SpringerVerlag, New York, 1979 in Chapter 4 which is incorporated herein byreference.

The photoresist compositions of this invention are prepared bydissolving the above-mentioned novolak or polyvinyl phenol resins andthe photosensitizer compositions of the invention in a solvent. Suitablesolvents for this purpose include, for example, propylene glycol methylether acetate and the like; glycol ethers such as ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether and the like;cellosolve acetates such as methyl cellosolve acetate, ethyl cellosolveacetate and the like; esters such as ethyl acetate, butyl acetate andthe like; ketones such as methyl ethyl ketone, cyclopentanone,cyclohexanone and the like; and aromatic hydrocarbons such as toluene,xylene and the like. It is also possible to use mixtures thereof. Thechoice of solvent, or mixture of solvents, will depend upon the coatingmethod intended, layer thickness, drying conditions and consideration ofthe solubilities of the constituents, vaporization speed of solventafter coating the photoresist composition on a substrate, and the like.

Optionally, additives such as colorants, dyes, anti-striation agents,plasticizers, adhesion promoters, speed enhancers and such surfactantsas non-ionic surfactants may be added to the photoresist compositionbefore it is coated onto a substrate.

In the preferred embodiments, the solid parts of the photoresistcompositions, that is the novolak or polyvinyl phenol resin andphotosensitizer composition, preferably ranges from 15% to about 99%novolak or polyvinyl phenol binder resin and from about 1% to about 85%photosensitizer composition. A more preferred range of binder resinwould be from about 50% to about 97% and most preferably from about 65%to about 93% by weight of the solid resist parts. A more preferred rangeof photosensitizer composition would be from about 3% to about 50% andmost preferably from about 7% to about 35% by weight of the solid resistparts. In preparing the resist composition the binder resin andphotosensitizer composition are mixed with the solvent such that thesolvent is present in an amount of from about 40% to about 90% by weightof the overall resist composition. A more preferred range is from about60% to about 85% and most preferably from about 65% to about 80% byweight of the overall resist composition.

Examples of dye additives that may be used together with the photoresistcompositions of the present invention include Methyl Violet 2B (C.I. No.42535), Crystal Violet (C.I. 42555), Malachite Green (C.I. No. 42000),Victoria Blue B (C.I. 44045) and Neutral Red (C.I. No. 50040) at one toten percent weight levels, based on the combined weight of novolak andsensitizer. The dye additives help provide increased resolution byinhibiting back scattering of light off the substrate.

Anti-striation agents may be used up to five percent weight level, basedon the combined weight of novolak and sensitizer.

Plasticizers which may be used include, for example, phosphoric acidtri-(β-chloroethyl)-ester; stearic acid; dicamphor; polypropylene;acetal resins; phenoxy resins; and alkyl resins at one to ten percentweight levels, based on the combined weight of novolak and sensitizer.The plasticizer additives improved the coating properties of thematerial and enable the application of a film that is smooth and ofunifiorm thickness to the substrate.

Adhesion promoters which may be used include, for example,β-(3,4-epoxy-cyclohexyl)-ethyltrimethoxysilane; p-methyl-disilane-methylmethacrylate; vinyltrichlorosilane; and γ-amino-propyl triethoxysilaneup to a 4 percent weight level, based on the combined weight of novolakand sensitizer.

Speed enhancers that may be used include, for example, picric acid,nicotinic acid or nitrocinnamic acid at a weight level of up to 20percent, based on the combined weight of novolak and sensitizer. Theseenhancers tend to increase the solubility of the photoresist coating inboth the exposed and unexposed areas, and thus they are used inapplications when speed of development is the overriding considerationeven though some degree of contrast may be sacrificed; i.e., while theexposed areas of the photoresist coating will be dissolved more quicklyby the developer, the speed enhancers will also cause a larger loss ofphotoresist coating from the unexposed areas.

Non-ionic surfactants that may be used include, for example,nonylphenoxy poly(ethyleneoxy)ethanol; octylphenoxy(ethyleneoxy)ethanol;and dinonyl phenoxy poly(ethyleneoxy)ethanol at up to 10 percent weightlevels, based on the combined weight of novolak and sensitizer.

Solution Stability

Photoresist compositions were prepared according to the method outlinedabove. The photosensitizer compositions from the examples are dissolvedin a prefiltered solution of 24.0% novolak resin and 76% propyleneglycol methyl ether acetate (PGMEA). The resist compositions areadjusted to a sensitizer absorptivity of 1.0 l/gm-cm at a wavelength of377 nm. For example, if 30 mg sample of2,3,4-trihydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acidtriester in one liter of acetone has an absorptivity of 0.731 asmeasured at 377 nm, the resist composition is prepared as follows:

4.1% photosensitizer composition

23.0% novolak resin

72.9% PGMEA

As a second example, if a 30 mg sample of a photosensitizer compositionin a liter of acetone has a absorptivity of 0.681, the resistcomposition is prepared as follows:

4.4% photosensitizer composition

22.9% novolak resin

72.7% PGMEA

The thusly prepared photoresist test solutions are filtered through anErtel grade 8 filter pad, then through a 0.2 to 0.5 μm Fluoropore filter(available from Millipore Corporation). The test solutions are protectedfrom light and stored in a constant temperature air oven at 50° C. for aperiod of five days and then examined for visible precipitate. Ifprecipitate is visible in a test solution, the sample has failed thesolution stability test. Results from the solution stability test forseveral modified and unmodified photosensitizer compositions are setforth in Table 1.

                  TABLE 1                                                         ______________________________________                                        Photosensitizer                                                                          Modification.sup.1                                                                           Solution Stability                                  Sample     (mole %)       Test Result                                         ______________________________________                                        A          none           Fail                                                B          none           Fail                                                C          none           Fail                                                D          2.5% methanesulfonyl                                                                         Pass                                                           chloride                                                           E          2.5% methanesulfonyl                                                                         Pass                                                           chloride                                                           F          5% methanesulfonyl                                                                           Pass                                                           chloride                                                           G          5% methanesulfonyl                                                                           Pass                                                           chloride                                                           H          10% methanesulfonyl                                                                          Pass                                                           chloride                                                           I          10% methanesulfonyl                                                                          Pass                                                           chloride                                                           J          10% methanesulfonyl                                                                          Pass                                                           chloride                                                           K          20% methanesulfonyl                                                           chloride                                                           L          20% methanesulfonyl                                                                          Pass                                                           chloride                                                           M          10% ethanesulfonyl                                                                           Pass                                                           chloride                                                           N          10% benzenesulfonyl                                                                          Pass                                                           chloride                                                           O          10% valeryl chloride                                                                         Pass                                                P          10% dichlorobenzoyl                                                                          Pass                                                           chloride                                                           ______________________________________                                         .sup.1 The photosensitizer compositions of the test samples were prepared     by reacting 2,3,4trihydroxybenzophenone with a stoichiometric amount of a     Diazo/organic acid halide mixture. The figures in this column represent       the percentage of organic acid halide in the mixture. In samples where no     modification was made, the 2,3,4trihydroxybenzophenone was condensed with     only Diazo.                                                              

As the data indicates, the modified photosensitizer compositions haveimproved solution stability over the unmodified photosensitizers.

Several other phenolic compounds were modified. However, the solutionstability testing data are inconclusive because the photosensitizercomposition could not be formulated in the stock resin solutiondescribed above or both the modified and unmodified compositions failedthe test. The data are set forth in Table 2.

                  TABLE 2                                                         ______________________________________                                                                           Solution                                   Photosensitizer                                                                         Phenolic    Modification Stability                                  Sample    Compound    (mole %)     Test Result                                ______________________________________                                        Q         1,3,5-trihydroxy                                                                          none         Unable to                                            benzene                  Formulate                                  R         1,3,5-trihydroxy                                                                          10% methane- Unable to                                            benzene     sulfonyl chloride                                                                          Formulate                                  S         2,2',4,4'-tetra-                                                                          none         Fail                                                 hydroxybenzo-                                                                 phenone                                                             T         2,2',4,4'-tetra-                                                                          10% methane- Fail                                                 hydroxybenxo-                                                                             sulfonyl chloride                                                 phenone                                                             ______________________________________                                    

The choice of the solvent system may affect the ability to formulate aparticular photosensitizer composition. For example, a photosensitizermay be difficult to formulate in one solvent system, but readilyformulated in another. However, where the modified and unmodifiedphotosensitizer compositions can be formulated, the unmodifiedcomposition will generally precipitate before the modified composition.

Shelf Life

Determining the shelf life at room temperature for a particular samplephotoresist composition is both time-consuming and impractical. Thesolution stability test, as described previously, is preferred forpredicting the relative shelf life anticipated for a resist compositionprepared from a particular photosensitizer composition. However, realtime shelf life tests were done for several sample photoresistcompositions. The samples are stored at room temperature and areperiodically examined for any visible precipitate. Generally, theunmodified diazo photosensitizer precipitates from solution within sixweeks and nearly always before three months. Test data for samples afterthree months storage are set forth in Table 3.

                  TABLE 3                                                         ______________________________________                                        Photosensitizer                                                                          Modification.sup.1                                                                           Solution Stability.sup.2                            Sample     (mole %)       Test Result                                         ______________________________________                                        B          none           Fail                                                U          none           Fail                                                V          none           Fail                                                F          5% methanesulfonyl                                                                           Pass                                                           chloride                                                           G          5% methanesulfonyl                                                                           Pass                                                           chloride                                                           H          10% methanesulfonyl                                                                          Pass                                                           chloride                                                           I          10% methanesulfonyl                                                                          Pass                                                           chloride                                                           J          10% methanesulfonyl                                                                          Pass                                                           chloride                                                           K          20% methanesulfonyl                                                                          Pass                                                           chloride                                                           L          20% methanesulfonyl                                                                          Pass                                                           chloride                                                           ______________________________________                                         .sup.1 The photosensitizer compositions of the test samples were prepared     by reacting 2,3,4trihydroxybenzophenone with a stoichiometric amount of a     Diazo/organic acid halide mixture. The figures in this column represent       the percentage of organic acid halide in the mixture. In samples where no     modification was made, the 2,3,4trihydroxybenzophenone was condensed with     only Diazo.                                                                   .sup.2 The samples were examined after three months. "Fail" denotes           visible precipitation observed, "Pass" denotes no visible precipitation. 

The data indicates that relative to the unmodified Diazophotosensitizer, the modified sensitizer compositions of the inventionhave an enhanced resistance to precipitation and, consequently,photoresist compositions formulated therefrom have longer shelf lifes.

Photosensitivity, Contrast and Unexposed Film Loss

The prepared resist solution, can be applied to a substrate by anyconventional method used in the photoresist art, including dipping,spraying, whirling and spin coating. When spin coating, for example, theresist solution can be adjusted as to the percentage of solids contentin order to provide coating of the desired thickness given the type ofspinning equipment utilized and the amount of time allowed for thespinning process. Suitable substrates include silicon, aluminum orpolymeric resins, silicon dioxide, doped silicon dioxide, siliconnitride, tantalum, copper, polysilicon, ceramics and aluminum/coppermixtures.

The photoresist coatings produced by the above described procedure areparticularly suitable for application to thermally grown silicon/silicondioxide-coated wafers such as are utilized in the production ofmicroprocessors and other miniaturized integrated circuit components. Analuminum/aluminum oxide wafer can be used as well. The substrate mayalso comprise various polymeric resins especially transparent polymerssuch as polyesters.

After the resist composition solution is coated onto the substrate, thesubstrate is baked at approximately 80° to 105° C. until substantiallyall the solvent has evaporated and only a thin coating of photoresistcomposition on the order of a micron in thickness remains on thesubstrate. The coated substrate can then be exposed to actinic radiationespecially ultraviolet radiation in any desired exposure patternproduced by use of suitable masks, negatives, stencils, templates, etc.

The exposed resist-coated substrates are next substantially immersed inalkaline developing solution. The solution is preferably agitated, forexample, by nitrogen burst agitation.

The substrates are allowed to remain in the developer until all, orsubstantially all, of the resist coating has dissolved from the exposedareas.

After removal of the coated wafers from the developing solution, apost-development heat treatment or bake may be employed to increase thecoating's adhesion and chemical resistance to etching solutions andother substances. The post-development heat treatment can comprise theoven baking of the coating and substrate below the coating's softeningpoint. In industrial applications, particularly in the manufacture ofmicrocircuitry units on silicon/silicon dioxide-type substrates, thedeveloped substrates may be treated with a buffered, hydrofluoric acidbase etching solution. The resist compositions of the present inventionare resistant to acid-base etching solutions and provide effectiveprotection for the unexposed resist-coating areas of the substrate.

The following specific examples will provide detailed illustrations ofthe methods of producing and utilizing compositions of the presentinvention. These examples are not intended, however, to limit orrestrict the scope of the invention in any way and should not beconstrued as providing conditions, parameters or values which must beutilized exclusively in order to practice the present invention.

EXAMPLE 2

Resist formulations are prepared with the photosensitizer compositionsof this invention and adjusted to a sensitizer absorptivity of 0.761/gm-cm ±0.025 at a wavelength of 377 nm. The sensitizer to be tested isdissolved in a pre-filtered stock solution of 24.0% novolak resin and76% propylene glycol methyl ether acetate. The resist solutions are thenfiltered through an Ertel grade 8 filter pad.

The photoresist compositions are spin coated on several silicon wafersat a constant, predetermined spin speed to obtain 2.0 μm layers of driedresist film. The wafers are then baked at 90° C. for 30 minutes.

The initial film thicknesses of the resist coatings are measured by aRudolf Film Thickness Monitor. The wafers are then exposed to variedamounts of UV light energy (350-450 nm). The resists are developed for 1minute at 25° C. using AZ 400K alkali developer, available from AmericanHoechst Corporation, Somerville, N.J., diluted 1:3 with deionized water.At this developer strength, the dark erosion rate, or development rateof non-exposed resist film, is generally maintained within the range of0.005 to 0.015 μm/minute (50 to 150 Å/min.). The remaining filmthicknesses are then remeasured by the Rudolf Film Thickness Monitor todetermine film loss for the particular energy dose.

Photosensitivity is measured by generating a characteristic curve, asdescribed in Wake, R. W. and Flanigan, M. C., "A Review of Contrast inPositive Photoresists", SPIE Vol. 539, Advances in Resist Technology andProcessing II (1985), p. 291, which is herein incorporated by reference,wherein film thickness loss after one minute of development is plottedagainst the logarithm of the UV exposure dose. By interpolation of thisplot to 1.0 μm film loss, the photosensitivity value in mJ/cm² isobtained. The slope of the linear portion of the plot is the contrast.

The results of photosensitivity, contrast and dark erosion rate testingof several photoresist compositions prepared with photosensitizercompositions of this invention are set forth in Table 4 and comparedwith photoresists prepared with unmodified photosensitizer compositions.Statistical standards were established by testing three samples offormulated resists containing unmodified2,3,4-trihydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid(Diazo) triester. Each sample was evaluated three times forphotosensitivity and contrast, thus generating nine sets of data. Therange of deviation in photosensitivity (mJ/cm²) from the mean photospeedwas ±10 percent. The absolute difference between the high and lowphotosensitivity values was 20 percent of the low value. Similarly, therange of deviation in the contrast values from the mean contrast valuewas ±10 percent and the absolute difference between the high and lowcontrast value was 24 percent of the low value.

                                      TABLE 4                                     __________________________________________________________________________                                  Dark  Photosensitivity (%                       Photosensitizer                                                                       Modification                                                                              Absorptivity                                                                            Erosion                                                                             faster (-).sup.1 or slower                                                                 Contrast (% higher (+)                                                        or.sup.2                     Sample  (mole %)    (1/gm-cm @ 377 nm)                                                                      (μm/min.)                                                                        of standard) lower (-) than               __________________________________________________________________________                                                     standard)                    D       2.5% methane-                                                                             0.762     0.007 +4            0                                   sulfonyl chloride                                                     F       5% methane- 0.759     0.011 +22          +15                                  sulfonyl chloride                                                     G       5% methane- 0.782     0.009 +13          +16                                  sulfonyl chloride                                                     H       10% methane-                                                                              0.758     0.006 -3           +3                                   sulfonyl chloride                                                     I       10% methane-                                                                              0.752     0.003 +8           -3                                   sulfonyl chloride                                                     J       10% methane-                                                                              0.778     0.001 +6           -2                                   sulfonyl chloride                                                     K       20% methane-                                                                              0.775     0.005 +43          +23                                  sulfonyl chloride                                                     L       20% methane-                                                                              0.770     0.006 +54          +18                                  sulfonyl chloride                                                     M       10% ethane- 0.756     0.011 +16          +12                                  sulfonyl chloride                                                     N       10% benzene-                                                                              0.775     0.007 +39          +6                                   sulfonyl chloride                                                     O       10% valeryl-                                                                              0.770     0.010 +29          -17                                  sulfonyl chloride                                                     P       10% dichlorobenzoyl-                                                                      0.767     0.008 +38          -15                                  sulfonyl chloride                                                     __________________________________________________________________________     .sup.1 Typical photosensitivity of standard                                   2,3,4trihydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid         triester                                                                      @ 350-450 nm broadband exposure measured at 405 nm = 18.9 mJ/cm.sup.2         @ 365 nm narrowband exposure measured at 365 nm = 20.6 mJ/cm.sup.2            .sup.2 Typical contrast values of standard                                    2,3,4trihydroxybenzophenone-1,2-naphthoquinonediazide-4-sulfonic acid         triester                                                                      @ 350-450 nm broadband exposure measured at 405 nm = 3.09                     @ 365 nm narrowband exposure measured at 365 nm = 2.43                   

What is claimed is:
 1. A photoresist composition having improvedsolution stability comprising an admixture of a novolak or polyvinylphenol resin, a solvent and a photosensitizer composition comprising thecondensation product of:I. A phenolic compound having the structure:##STR37## wherein: R_(a) is H, OH, halogen or lower alkyl, with at leasttwo and not greater than six R_(a) radicals being OH, and X is a singleC--C bond, --O--, --S--, --SO₂ --, ##STR38## n is 1 or 2, II. A 1,2naphthoquinonediazide-4-sulfonic acid (Diazo); and III. An organic acidrepresented by the formula

    W--R.sub.3

wherein W is ##STR39## or --SO₂ --V, V is halogen and R₃ is alkyl, aryl,substituted alkyl or substituted aryl; wherein the molar ratio of theamount of Diazo reacted to the amount of organic acid reacted is in therange of from about 1:1 to about 39:1, and the amount of Diazo andorganic acid reacted with said phenolic compound being sufficient toproduce a photosensitizer composition capable of inhibiting thedissolution rate of an alkali soluble resin in alkaline developingsolution.
 2. A photoresist composition having improved solutionstability comprising an admixture of novolak or polyvinyl phenol resin,a solvent and a photosensitizer composition comprising the condensationproduct of:I. A phenolic compound having the structure: ##STR40##wherein: R_(a) is H, OH, halogen or lower alkyl, with at least two andnot greater than six R_(a) radicals being OH; II. A 1,2naphthoquinonediazide-4-sulfonic acid (Diazo); and III. An organic acidhalide represented by the formula:

    W--R.sub.3

wherein W is ##STR41## or --SO₂ --V, V is halogen and R₃ is alkyl, aryl,substituted alkyl or substituted aryl; wherein the molar ratio of theamount of Diazo reacted to the amount of organic acid reacted is in therange of from about 1:1 to about 39:1, and the amount of Diazo andorganic acid reacted with said phenolic compound being sufficient toproduce a photosensitizer composition capable of inhibiting thedissolution rate of an alkali soluble resin in alkaline developingsolution.
 3. The composition of claim 2 containing from about 50% toabout 97% by weight resin and from about 3% to about 50% by weightphotosensitizer on a solids basis, mixed with solvent present in anamount of about 40% to 90% by weight of the overall composition.
 4. Thecomposition of claim 3 wherein the amount of resin is from about 65% toabout 93% by weight, the amount of photosensitizer is from about 7% toabout 35% by weight, and the solvent is mixed in an amount of about 65%to about 80% by weight.
 5. A photoresist composition according to claim2, wherein said ratio of said amount of Diazo reacted to said amount oforganic acid halide reacted is in the range of from about 4:1 to about19:1.
 6. A photoresist composition according to claim 5, wherein saidphenolic compound is a dihydroxybenzophenone, a trihydroxybenzophenoneor a tetrahydroxybenzophenone; and said organic acid halide is a loweralkyl sulfonyl halide, a benzene sulfonyl halide, a lower alkyl acylhalide or a benzoyl halide.
 7. A photoresist composition according toclaim 5, wherein said phenolic compound is 2,3,4-trihydroxybenzophenone.8. A photoresist composition according to claim 7, wherein said solventis propylene glycol methyl ether acetate.
 9. A photoresist compositionaccording to claim 2, wherein said ratio of said amount of Diazo reactedto said amount of organic acid halide reacted is in the range of fromabout 93:7 to about 85:15.
 10. A photoresist composition according toclaim 9, wherein said phenolic compound is a dihydroxybenzophenone, atrihydroxybenzophenone or a tetrahydroxybenzophenone; and said organicacid halide is a lower alkyl sulfonyl halide, a benzene sulfonyl halide,a lower alkyl acyl halide or a benzoyl halide.
 11. A photoresistcomposition according to claim 9, wherein said phenolic compound is2,3,4-trihydroxybenzophenone.
 12. A photoresist composition according toclaim 11, wherein said solvent is propylene glycol methyl ether acetate.13. A photoresist composition according to claim 2, wherein saidphenolic compound is a dihydroxybenzophenone, a trihydroxybenzophenoneor a tetrahydroxybenzophenone; and said organic acid halide is a loweralkyl sulfonyl halide, a benzene sufonyl halide, a lower alkyl acylhalide or a benzoyl halide.
 14. A photoresist composition according toclaim 2, wherein said phenolic compound is 2,3,4-trihydroxybenzophenone.15. A photoresist composition according to claim 14, wherein saidsolvent is propylene glycol methyl ether acetate.
 16. A method forproducing an article which comprises coating a photoresist compositioncomprising a novolak or polyvinyl phenol resin, a solvent and aphotosensitizer composition according to claim 2 onto a substrate;imagewise exposing said composition to sufficient ultraviolet radiationto render said imagewise exposed portions substantially soluble in anaqueous alkaline solution; and then removing the thusly exposedcomposition portions from said substrate with an aqueous alkalinedeveloping solution.